Isolation and X-ray structure analysis of citreohybridonol from marine-derived Penicillium atrovenetum

The anti-neuroinflammatory meroterpenoid citreohybridonol was isolated for the first time from a sponge-derived fungus Penicillium atrovenetum. In this study, in addition to isolation and structure featuring, its unambiguous absolute configuration was determined exclusively by single crystal X-ray diffraction. The C-17-keto tautomer was clearly observed in X-ray analysis. The substance crystallises in the monoclinic space group P2₁ with a = 10.7496(5) Å, b = 14.3286(7) Å, c = 17.4909(8) Å, β = 103.235(2)°, V = 2622.5(2) Å³, Z = 2, D_calcd = 1.280 g/cm³. The chirality of the asymmetric carbon atoms was as follows: C3 (S), C5 (R), C6 (S), C8 (S), C9 (R), C10 (R), C13 (R), C14 (R).     

2D → 3D corrugated structure self-assembled from 4,4′-methylenebis(N-(pyridin-2-ylmethylene)aniline and terephthalic acid: Crystal structure and selective anion separations via anion exchange

A new flexible cationic Zn(II)metal organic framework, {[Zn₂(BDC)_1.5(L)(DMF)]NO₃·DMF·solvent}_n, MOF 1 , which is a corrugated two-dimensional network, was synthesized by self-assembly of Zn(NO₃)₂.6H₂O with 4,4′-methylenebis(N-(pyridin-2-ylmethylene)aniline as a neutral ligand and terephthalic acid in dimethyl formamide (DMF) as solvent and characterized by X-ray diffraction. Because of the presence of uncoordinated nitrate (NO₃⁻) ions in the channels, the compound was employed for ion-exchange applications. We report a detailed study of the host–guest interaction for a cationic metal–organic framework (MOF) that can reversibly capture nitrate. The recrystallization of the MOF was evaluated by monitoring the anion exchange dynamics using a combination of powder X-ray diffraction and Fourier transform infrared spectra with various kinds of foreign anions. This MOF showed fast and highly efficient Cr₂O₇²⁻ and CrO₄²⁻, N₃⁻, MnO₄⁻, and SCN⁻ exchange. The trapping capacities of Cr₂O₇²⁻, CrO₄²⁻, N₃⁻, MnO₄⁻, and SCN⁻ were 105,138, 44,104, and 25mg/g at 25°C after 3h, respectively, and there was good recyclability for capturing N₃⁻ and SCN⁻. {[Zn₂(BDC)_1.5(L)(DMF)]NO₃}_n exhibited anion exchange selectivity of SCN⁻ in a solution containing a mixture of 0.025mmol N₃⁻, SCN⁻, CrO₄⁻²⁻, Cr₂O₇²⁻, and MnO₄⁻ for 3h and exhibited anion exchange selectivity for SCN⁻ and Cr₂O₇²⁻ in a solution containing a mixture of 0.001mmol N₃⁻, SCN⁻, CrO₄²⁻, Cr₂O₇²⁻, and MnO₄⁻.     

Sequential Cu-Catalyzed Four- and Five-Component Syntheses of Luminescent 3-Triazolylquinoxalines

3-Triazolylquinoxalines can be readily synthesized by applying two complementary synthetic protocols starting from heterocyclic π nucleophiles or (hetero)aryl glyoxylic acids in a consecutive four- or five-component reaction. Conceptually, the sequential use of a single cuprous salt for alkynylation and Cu-catalyzed alkyne-azide cycloaddition (CuAAC) in a one-pot fashion sets the stage for activation-alkynylation-cyclocondensation-CuAAC or glyoxylation-alkynylation-cyclocondensation-CuAAC sequences in good yields. The diversity-oriented generation of differently substituted 3-triazolylquinoxalines is an excellent entry to tunable emission solvatorchromic fluorophores with triazole ligation. The electronic structure, corroborated by DFT and TD-DFT calculations, rationalizes the charge transfer character of relevant absorptions and large Stokes shifts as well as the electronic innocence of the triazole substituents.     

Gas Flow Dynamics in Inlet Capillaries: Evidence for non Laminar Conditions

In this work, the characteristics of gas flow in inlet capillaries are examined. Such inlet capillaries are widely used as a first flow restriction stage in commercial atmospheric pressure ionization mass spectrometers. Contrary to the common assumption, we consider the gas flow in typical glass inlet capillaries with 0.5 to 0.6 mm inner diameters and lengths about 20 cm as transitional or turbulent. The measured volume flow of the choked turbulent gas stream in such capillaries is 0.8 L·min^?1 to 1.6 L·min^?1 under typical operation conditions, which is in good agreement to theoretically calculated values. Likewise, the change of the volume flow in dependence of the pressure difference along the capillary agrees well with a theoretical model for turbulent conditions as well as with exemplary measurements of the static pressure inside the capillary channel. However, the results for the volume flow of heated glass and metal inlet capillaries are neither in agreement with turbulent nor with laminar models. The velocity profile of the neutral gas in a quartz capillary with an inner diameter similar to commercial inlet capillaries was experimentally determined with spatially resolved ion transfer time measurements. The determined gas velocity profiles do not contradict the turbulent character of the flow. Finally, inducing disturbances of the gas flow by placing obstacles in the capillary channel is found to not change the flow characteristics significantly. In combination the findings suggest that laminar conditions inside inlet capillaries are not a valid primary explanation for the observed high ion transparency of inlet capillaries under common operation conditions.

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Are Clusters Important in Understanding the Mechanisms in Atmospheric Pressure Ionization? Part 1: Reagent Ion Generation and Chemical Control of Ion Populations

It is well documented since the early days of the development of atmospheric pressure ionization methods, which operate in the gas phase, that cluster ions are ubiquitous. This holds true for atmospheric pressure chemical ionization, as well as for more recent techniques, such as atmospheric pressure photoionization, direct analysis in real time, and many more. In fact, it is well established that cluster ions are the primary carriers of the net charge generated. Nevertheless, cluster ion chemistry has only been sporadically included in the numerous proposed ionization mechanisms leading to charged target analytes, which are often protonated molecules. This paper series, consisting of two parts, attempts to highlight the role of cluster ion chemistry with regard to the generation of analyte ions. In addition, the impact of the changing reaction matrix and the non-thermal collisions of ions en route from the atmospheric pressure ion source to the high vacuum analyzer region are discussed. This work addresses such issues as extent of protonation versus deuteration, the extent of analyte fragmentation, as well as highly variable ionization efficiencies, among others. In Part 1, the nature of the reagent ion generation is examined, as well as the extent of thermodynamic versus kinetic control of the resulting ion population entering the analyzer region.